A conventional hand tool with a driving head can be optionally connected with an extension rod, an adaptor and different shapes of bits. The driving head generally includes a connection end and an engaging end, wherein the connection end is connected to the bits for example and the engaging end is connected with the hand tool such as a wrench.
U.S. Pat. No. 5,477,434 discloses an extension bar with a built-in light and a power supply unit, when the hand tool is connected to the extension bar, the built-in light and the power supply unit are activated so as to form the circuit. However, the circuit cannot be activated by a switch when the hand tool is removed from the extension bar, in other words, the built-in light cannot be individually used as a flashlight and is restricted.
U.S. Pat. No. 6,183,103 discloses an extension bar with selective illumination, wherein the two illumination members are located on two sides of the extension bar and a switch is available on the extension bar, wherein two non-conductive members are connected to two ends of the switch which cut off the circuit when the non-conductive members are in contact with the illumination members. When the conductive portion of the switch is in contact with the illumination member, the circuit is formed so that the extension bar can be individually used as a flashlight. When the driving head of a wrench is connected to the extension bar, the illumination member can also be activated by operation of the switch. However, it the inconvenient for the user because the illumination member has to be activated by operation of the switch when the driving head of a hand tool is connected to the extension bar.
The present invention intends to provide an extension bar which includes a body, a conductive unit, a control unit and an illumination unit, wherein the user can operates the control unit to directly control the illumination unit. The control unit can be easily removed from the body to replace parts therein. The illumination unit can be automatically activated when the extension bar is connected with a hand tool.